Circuit breaker



Hf D. DoRFMAN rs1-AL.

CIRCUIT BREAKER Filed May 9, 1941 March 28, 1944.

2 Sheets-Sheet 1 ATIORNE H. D. DORFMAN ET- AL CIRCUIT BREAKER March 28, 1944.

Filed May 9, 1941 2 Sheets-Sheet 2 44 55 F/g. 5 o

45 n? jvv 46 if 4f 32 55 5262 33 58 3 6o 6/ /C v I :732

fz 55 62 V5 WlTNvESSES:

ATTORNEY lar in the appended claims.

Patented Mar. 28, 1944 CIRCUIT BREAKER Hiller D. Dorfman, Forest Hills, and Lloyd W.

Dyer, Wilkinsburg, Pa.,'assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Penn- *r sylvania y,

Application May 9, 1941, Serial No. 392,664

24. Claims. (Cl. 20o- 88) This invention relates to circuit breakers, and more particularly relates to circuit breakersy of the type which are automatically operated instantaneously on heavy overload currents above a predetermined magnitude, and after a time delay on sustained overloads of lesser magnitude.

It is an object of the instant invention to provide a circuit breaker having an improved snapacting trip device.

Another object of the invention is the provision of a circuit breaker having a simplified thermally and magnetically responsive trip device.

Another object of the invention is the provision in a circuit breaker of a novel snap-acting toggle which includes a thermally responsive element as an operative part of the gle.

A further object of the inven on is the provision of a circuit breaker having a releasing member biasedby opposed forces and a novel snap-acting toggle, including as an operative part thereof a thermally responsive element for re-f ducing one Aof 'the forces to permit the other force to operate thereleasing member.

Still another object of the instant invention is the provision of a circuit breaker having a trip member biased by opposed springs wherein the force exerted by one of the springs is controlled Y by a thermally responsive bimetal disk.

In carrying the invention into effect, the latch member, which restrains the breaker operating mechanism in closed circuit position, is biased in opposite directions by springs which normally exert substantially equal forces on the latch, the springs thus normally balancing each other. One of thesprings is controlled by a thermalLv responsive element which. `when heated by the current of the circuit controlled by the breaker, acts Fig. 2 illustrates the same mechanism shown in Fig. i, but inthe tripped open position:

Fig. 3 is a fragmentary view. partly in section. showing a modified form of tripping mechanism in latched position;

Fig. 4 is a view similar to Fig. 3 showing the mechanism in tripped position; and

Fig.v 5 isv a detail view of another modiilction of lthe thermally responsive tripping element.

The several elements comprising the circuit breaker are mounted on an insulating base I3.

A pair of terminals Il and I2 secured on opposite ends of the base serve to electrically connect the breaker inv the circuit to be controlled thereby. The terminal Il carries a stationary contact I3, which cooperates with a movable contact I4 carried on a spring arm I5 secured to the free end the base I0. Between the upper ends of arms to reduce the force exerted by one of the springs and thereby cause tripping of the breaker. A series overload electromagnet also exerts a force' on the latch tending to release the latch.

The novel features that are considered characteristic of the invention are set` forth in particu- The invention itself, however. both as to structure and operation. together with additional objects and advantages thereof, will be best understood from the following detailed description of several embodiments thereof when read in commotion with the accompanying drawings. in which:

Figure 1 is a view in side elevation of the circuit breaker with the casing'removed and in the closed contact position;

of the contact arm I3. The contact arm Il is mountedon a pivot i1 extending between arms I3 and i3 .of a U-shaped bracket 20 secured to pivoted a manually operable handle 22 and a releasable lever 23. Toggle links 24 and 2l pivotally connected, respectively, to the end of the yreleasable lever 23 andthe contact arm Il, are connected by a knee pivot 23. A link 21 has one end connected to the links 24 and 2lat their knee pivot 2l, and the opposite end of the link 21 is provided with a' slot z-embracing a stud 2l projecting from the lower arm of the operating handie 22. A pair oi operating springs 3l (only one being shown) are disposed on opposite sides of the linkage and tensioned between the iixed pivot 2i and a projection 3| on the contact arm Il. The springs 30 bias the contact arm I3 to open circuit position.

The releasable lever 23 is normally retained in the position shown in Fig. l to normally pro vide a xed support ior the outer end of the toggle 2,4-25, by a latch 32 carried by an extension 33 ofagmagnet armature 34 forming part of a trip device. The armature 34 is pivotally mounted on one leg of-a U-shaped magnet core as which has its other ieg :s secured to, but insulated from, a bracket 31 secured to the base Il.

A thermally responsive bimetai-1 element` 33' the bent portion 33 oi the bimetal element 33. The portion 33 is bent downwardly to form an angle oi less than 90 with the vertical portion of the bimetal element. With the binietal in its normally cold state and during normal current conditions, the toggle, formed by the bimetal lportion 33 and the rod 4I, is over center below a line drawn fromr the bend of the bimetal through the center oi the opening in the armatui'e extension 33 through which the rod 4| passes. A stop stud 43 on the bracket 31 limits the overcenter movement oi the toggle.

The bimetal element 33--33 is connected in series with a coil 44 wound on one leg of the magnet core 33, and both are traversed by the current ci the circuit controlled by the breaker, the circuit extending from terminal il, contacts l3-I4, spring arm I3, contact arm I8, a flexible shunt conductor 43, coil 44, conductor 46, bimetal 33-33 to the terminal I2.

'Ihe amature 34 is biased in tripping direction by a spring 41 having one of its ends connected to the armature 34 and the other end connected to an adjusting screw 43 in the magnet core 3l. The force oi the spring 41 is substantially balanced by the force oi the spring 42 when the bimetal is cold and during normal current conditions. The screw 43 provides a convenient means whereby the tension of the spring 41vv may be changed to vary the tripping point or the breaker.

The trip device is unresponsive to normal current conditions in the circuit controlled by the breaker, but is operable in response to overload currents o! predetermined magnitude to eileet automatic opening of the contacts I3--I4 by re,

leasing the lever 23. i, Upon the occurrence of overloads above a predetermined magnitude, for example, in excess oi approximately i times rated current, and

` overloads such as are occasioned by short circuits, themagnet becomes immediately eilective to attract the amature 34 and release the lever 23. In this case the spring 42 compresses slightly without appreciably moving the bimetal ele-` ment 33-33. Overloads below a predetermined magnitude it continued, may cause serious damage to the circuit and/or devices operated thereby. 'I'he bimetal element 33--39 is thermally responsive to such continuous overioads,

and when heated thereby possesses the characteristic o! iiexing to substantially the shape disclosed in F18. 2. During this iiexing, the portion 33 oi the bimetal bends to the left, allowing the rod 4i and the armature 34 to follow, and, at the same time, the portion 33 bends upwardly carrying the headed rod 43-4I therewith away from stop 43. This decreases the force of the spring 42 opposing unlatching movement of the amature extension 33. When the tip of the portion 33 and the notched head 40 pass dead center, that is, when rod 4l passes a line perpendicular to the extension 33 of the armature, the resultant force of the movement oi the bimetalelment 33-39 and the tension of the spring 42 causes it to snap upwardly against a stop 33. As a result of this action, the force exerted by the spring 42 on the extension 33 is suddenly reduced and the spring 41 assisted by the pull of the electromagnet overcomes the spring 42, `moving the amature 34 and its extension 33 to unlatch the lever 23.

When the lever 23 is thus released, the operating "rings 33 act to move the contact arm I3, togg 24-23, and lever 23 to their tripped turn to normal without tripping the breaker.

If, however, the overload continues, the elements operate in the manner above set iorth to interrupt the circuit.

Before the contacts |3-,l4 can be closed following an automatic tripping operation, it is necessary iirst to restore the lever 23 to latched -the contacts I3-l 4.

position. This is eilected manually by clockwise movement of the handle 22 to its open position, that is, the extreme clockwise position of the handle. The link 21 transmits this movement ol the handle to the toggle links 24--25 which, Isince counter-clockwise movement of the contact arm IB is limited by a stop 43, brealn; the toggle and rocks the lever 23 clockwise to latching position where it is restrained by the latch 32. Counterclockwise movement of the handle 22 now straightens the toggle 24--23 and closes contacts |3|4. The toggle 24-23 is limited in its overcenter travel by a stud 3| projecting from link 24 which engages a projection on the end of the link 25.

The circuit may be interrupted manually by operation of the handle 22. With the parts in the positions in which they appear in Fig. i, the handle 22 is rotated clockwise. At this move- `ment the stud 23 strikes the end of the slot 2l in the link 21. This moves the link 21 toward the left (Fig. 1) and breaks the toggle 2425. The releasable member 23, in this case, provides a iixed pivot for the toggle link 24. Breaking ot the toggle 24-23 operates the arm I6 to open Counterclockwise movement of the handle 22 straightens the toggle 24-23 and recloses the contacts |3I4.

The modification of the invention illustrated in Figs. 3 and 4 makes use of a snap acting bimetal disk 52 to' cause operation o! the tripping device on overloads of less than the predetermined magnitude. The disk 32 is mounted in a cylindrical shell 33 against the inturned iiange,

34 oi the shell. A retainer sleeve I3 suitably secured in the shell 33 holds the disk 32 in place against the flange 34. The shell 33 is rigidly mounted on a vertically disposed insulating bar 33 secured to the base i3 by an angle member 31. Also secured to the bar t3 is a U-shaped heater element 33 projecting into the shell 33 and disposed substantially parallel to the disk 32. Terminals 53 (only one of which is shown) serve to electrically connect the heater element 33 in the circuit in series with the coil 44 of the magnet and in series with the circuit controlled by the breaker, so as to be traversed by the current of the circuit.

A rod 63 secured to the disk 32 by a lock nut projects loosely through the armature extension 33, and has a pin 6I secured transversely therein on the opposite side or the extension. A spring 32 compressed between the lock nut and the extension 33 balances the spring 41 which tends to bias the armature 34 to tripping position.

Upon the occurrence of an overload greater than a predetermined magnitude, lor example, greater than approximately 8 to i0 times rated current, the coil 44 energizes the magnet suiciently tocause it to attract its armature and thus release the lever 23 immediately irrespective of the position of the disc 52. The pull of the magnet on overloads of less than predetermined magnitude is normally insufiicient to move the amature to attracted position against the tension of the spring 62 when the disc 52 is in the position shown in Fig. 3. Such overload currents flowing through the heater element 58 heat th'e disk 52 until, due to the different coeillcients of expansion of the two metals comprising the disk B2, the disk suddenly snaps from the position shown in Fig. 3 to the position shown in Fig. 4. This snap action of the disk carries the rod 60 and, through the pin 6I, the extension 33 to the left, causing release of the lever 23 to automatically interrupt the circuit. The pull of the magnet increases as the magnitude of the current increases and acts to assist in snapping the bimetal disk, thus causing it to snap sooner than it would in the absence of the magnet in the case oi moderate and heavy overloads.

After the circuit is interrupted, the disk 52 cools to a predetermined point whereupon it snaps back to its original position shown in Fig. 3, restoring the latch element to latching position. The breaker may now be reset in the same manner'described in connection with the previously described embodiment. The other elements of the breaker are the same as in Fig. 1 and corresponding parts have been indlcated'by like reference numerals.

The modiiication disclosed in Fig. 5 omits the pin 6|.'4 In this embodiment of the invention, a longer rod 63 is provided, which rod projects a greater distance through the latch element 33 to insure that the rod does not become disengaged from the latch 33 during operation. The spring 62 of Fig. 5, as in the modification in Fig. 3, is oi' substantially the same strength as the spring 41, and consequently these springs balance each other. In this case the snap action of the disk 52 when heated by the element 53 suddenly reduces the biasing eiect of spring 62, whereupon spring 41 now having the greater strength and being aided by the pull of the magnet overcomes the spring 62 and operates the latch to release the operating mechanism. Reverse snapping of the bimetal disk asit cools, increases the tension of the spring 62 which restores thelatch `33 to latching position and reestablishes the balance between springs 41 and 82. On overloads above a predetermined magnitude, the amature 34 is attracted by the magnet to release the operating mechanism, the element 33 compressing the spring B2, without displacing the disk l2. The spring 82 when thus compressed is stronger than the spring 41 and acts to restore the armature 34 to latching position upon interruption of the circuit.

In each of the embodiments of the invention disclosed herein the tension of the spring 41 may guage of the appended claims be given as reason-l ably broad interpretation asthe prior art permits.

We claim asour lnventionr- Y Y 1. In a circuit breaker, the combination oi relatively movable contacts, releasable operating mechanism to open the contacts automatically, a

latch operable to release the operating mechanism, a trip device having one member of a toggle operatively associated therewith, and a thermally responsive element acting conJointly with the toggle member to form a somplete toggle, the thermally responsive element acting in response to predetermined circuit conditions to 'operate the toggle and effect release of the operating mechanism.

2. In a circuit breaker, the combination of relatively movable contacts, releasable operating mechanism to open the contacts, a latch operable to release the operating mechanism and a trip device comprising' a snap-acting toggle, one member of said toggle being thermally responsive to predetermined circuit conditions for effecting release of the operating mechanism.

3. In a circuit breaker, the combination of relatively movable contacts, releasable operating means to open the contacts automatically, a

latch movable' to release the operating mechanism, and a toggle including a bimetal element as one element of the toggle thermally responsive to predetermined abnormal circuit conditions to eiiect operation of the latch to release the operating mechanism.

4. In a circuit breaker, the combination of relatively movable contacts, releasable operating means to automatically open the contacts, al

vlatch movable to release the operating means,

be adjusted by turning the screw 48 to vary-the invention in accordance with the patent statutes,

it is to be understood that various changes and modifications may be made in the particular embodiments disclosed without departing from some of the essential features of the invention. It is desired, therefore, that the lan` means acting to release the latch, means normally biasing the latch to iatching position, and a toggle including a bimetal element as an `element thereof, said bimetal element being responsive to predetermined circuit conditions to operate said toggle and render the biasing means? ineffective. i

5. A circuit breaker comprising relatively movable contacts, releasable operating mechanis'm to cause automatic opening of the contacts, a'. latch movable to release the operating mechanism, a member operatively associated with the latch, said member forming a part of a toggle, biasing means intermediate the member` and the latch biasing the latch to latching position, means for releasing the latch, and a bimetal element cooperating with the toggle member to complete the toggle, said bimetal element being thermally responsive to predetermined abnormal circuit conditions for causing the toggle move and render the biasing means ineffective.- 1

6. A circuit breaker comprising relatively movable contacts, releasable operating mechanism to cause automatic operation of the contacts, a latch operable to release the operating mechanism, means biasing the latch to latching position, anda bimetal element ccacting with said biasing means to form a toggle, the bimetal element being thermally responsive to predeter' nism to cause automatic opening of the'contacts,

a latch operable to release the operating mecha'- nism, and a thermally responsive toggle to permit the latch to release the operating mechanism in response to predetermined abnormal circuit conditions.

8. A circuit breaker comprising relatively movable contacts, releasable operating mechanism to cause automatic opening of the contacts, restrainingmeans operable to release the operating means, means at all times applying a iorce tending to move the restraining means in releasing direction and a thermally responsive snap acting toggle to control the operation of the restraining means.

9. A circuit breaker comprising contacts biased to open position, a latchmovable to released position to eilect automatic opening of the contacts, means for moving said latch to released position, a member slidably associated with the latch, a spring on said slidable member disposed to restrain the latch in latching position, and a bimetal element operatively associated with the slidable member and the spring, said b'metal element being thermally responsive to predetermined abnormal circuit conditions to render the restraining means ineffective to restrain the latch in latching position and cause said latch to be moved to released position.

10. A circuit breaker comprinng relatively movable contacts, releasable operating mechanism to automatically open the contacts, means operable to release the operating mechanism, an electromagnet for operating the releasing means to effect automatic opening of the contacts on overloads above a predetermined magnitude, and a thermally responsive toggle operable to permit the electromagnet to release the operating mechanism on overloads below the predetermined magnitude.

ll. A circuit breaker comprising relatively movable contacts, releasable operating mecha-.. nism to automatically open the contacts, a latch movable to release the operating mechanism, a member operatively associated with the latch, said member having a recessed head, resilient means intermediate the member and the latch normally biasing said latch to latching position, and a bimetal element having its free end formed to cooperate with the recessed head, the bimetal element together with the member formin'g a toggle responsive to predetermined circuit conditions to eiect unlatching operation oi the latch.

l2. A circuit breaker comprising relatively movable contacts, releasable operating mechanism to automatically open the contacts, a pivoted latch movable to release the operating mechanism, means comprising an electromagnet acting to release the latch, a bimetal element having its free end formed over at substantially right angles to the main portion oi said element, a rod having one end provided with a notched head cooperating with the free end of the bimetal element to form a toggle and having its opposite end slidably associated with the latch, and a spring intermediate the toggle and the latch to normally bias the latch to latching position, the bimetal element being thermally responsive to predetermined abnormal circuit conditions to operate the toggle and reduce the biasing influence of the spring to effect operation of the latch.

i3. A circuit breaker comprising relatively movable contacts, releasable operating mechanism for automatically opening the contacts, means movable w release the operating mechanism, snap-acting means comprising a thermal element and a spring normally opposing releasing movement of said releasing means. the thermal element being responsive when heated a predetermined amount to reduce the force exerted on said releasing means, and means including an electromagnet acting to release the operating mechanism.

14. A circuit breaker comprising relatively movable contacts, operating mechanism releasable to automatically open said contacts, a latch operable to release the operating mechanism, a bimetal element disposed to be heated by the current traversingd the circuit controlled by the breaker, a member having one end cooperating with the bimetal, the other end of said member being operatively associated with the latch, and a spring intermediate the bimetal and the latch for biasing the latch to latching position, a portion of said spring being operatively associated with and movable with said bimetal element, said bimetal being responsive when heated a predetermined amount to ilex with a snap action to cause unlatching operation of the latch.

l5. A circuit breaker comprising relatively movable contacts, releasable operating mechanism for automatically opening the contacts, a pivoted vlatch movable to release the operating mechanism, a snap-acting bimetal disc disposed to be heated by the current traversing the circuit controlled by the breaker, said disc being responsive when heated a predetermined amount to operate the latch with a snap action, a spring intermediate the disc and the latch biasing the latch to latching position, a portion of said spring being operatively associated with and movable with said bimetal disc, and electromagnetic means responsive to overloads above a predetermined magnitude to operate the latch.

i6. A circuit breaker comprising relatively movable contacts, releasable operating mechanism for automatically opening said contacts, an armature operable to release the operating mechanism, an electromagnet responsive to overloads of a predetermined magnitude to operate the armature, a snap-acting bimetal disc disposed to be heated by overload currents, a spring intermediate the disc and the armature biasing the armature to restrain the operating mechanism, said bimetal disc when heated a predetermined amount moving with a snap action in a direction to reduce the force exerted by the spring, and a second spring opposing the first-mentioned spring for operating the armature to release the operating mechanism when the force exerted by the first-mentioned spring has been reduced.

i7. A circuit breaker comprising relatively movable contacts, releasable operating mechanism for automatically opening said contacts, restraining means operable to release the operating mechanism, means comprising an electromagnet energized by the current of the circuit, said electromagnet when energized acting to move the restraining means to releasing position, a snap acting device comprising a thermally responsive element disposed to be heated by abnormal currents traversing the circuit controlled by the breaker, and a spring acting to normally maintain the restraining means in restraining position, the thermally responsive element when heated a predetermined amount operating to reduce the -force exerted on the restraining means through said spring to permit the electromagnet to operate the restraining means to released position.

18. A circuit breaker comprising relatively movable contacts, releasable operating mechanism for automatically opening the contacts, a

latch operable to release the operating mechanism, a spring biasing the latch to unlatching position, a second spring biasing the latch to latching position against the biasing force of the first-mentioned spring, and a bimetal element coacting with the rst-mentioned spring to form a toggle thermally responsive to predetermined circuit conditions to control the effectiveness of the second-mentioned spring.

19. A circuit breaker comprising releasable operating mechanism for causing automatic operation of the breaker, a latch operable to release the operating mechanism, means acting to release the latch, a spring biasing the latch to latching position, a bimetal element coacting with the spring to form a toggle, said bimetal being thermally responsive to predetermined circuit conditions to reduce the force exerted by the spring and effect release of the operating mechanism.

20. A circuit breaker including releasable operating mechanism for causing automatic operation of the breaker, a latch operable to release the operating mechanism, a toggle including a bimetal element and a spring intermediate the bimetal element and the latch, said bimetal element being operable when heated a predetermined amount to cause operation of the toggle and thereby effect release of the latch.

21. A trip device for a circuit breaker comprising latch? ng means operable to trip the breaker, means comprising a spring acting to release the latching means, a second spring acting to maintain the latching means in latching position, and snap-acting time delay means responsive to overload currents in the circuit controlled by the breaker to reduce the force-applied to the latching means through said second named spring and permit the mst named spring to trip the breaker.

22. A trip device for a circuit breaker comprising a pivoted latch operable to trip the breaker,

means actingto move the latch to tripping position, a snap acting bimetal disc heated in response to the current oi the circuit controlled by the breaker and normally opposing movement of the latch to tripping position, said bimetal disc being operable when heated a predetermined amount in response to overload currents to cause the latch to trip the breaker.

23. A circuit breaker comprising releasable operating mechanism to cause automatic operation of the breaker, restraining means operable to releasethe operating mechanism, a snap acting device including a thermally responsive element disposed to be heated by abnormal currents traversing the circuit controlled by the breaker, a spring between the thermal element and the restraining means biasing the restraining means to restraining position, the thermally responsive element being responsive when heated `a predetermined amount to reduce the force applied to saidrestraining means through the spring, and an electromagnet to operate the restraining means.

24. A circuit breaker comprising releasable operating mechanism to cause automatic operation of the breaker, a latch operable to release the operating mechanism, means acting to release the latch, a bimetal element disposed to be heated by the current traversing the circuit controlled by the breaker, and a spring intermediate the bimetal and the latch biasing the latch to latching position, a portion of said spring being operatively associated with and movable with said bimetal element, said bimetal being responsive when heated a predetermined amount to flex with a snap action to cause operation of the latch.

HILLER D. DORFMAN. LLOYD W. DYER. 

